1. Field of the Invention
The present invention relates to a high strength and high hardness alumina-zirconia-silicon carbide sintered ceramic composite and its manufacturing process.
2. Description of the Invention
Among other kinds of ceramics, alumina ceramics have been used in a variety of applications, for example, IC substrates, packages, cutting tools, etc.
On the other hand, in recent years there have been attempts to incorporate, partially stabilized zirconia into alumina, silicon carbide, silicon nitride, or other ceramic materials so that the sintered ceramic composites retain the high temperature tetragonal phase of zirconia at room temperature below the unconstrained transformation temperature. In these attempts, it was expected that the residual compressive stress due to a 4% volume increase accompanied by stress induced transformation of zirconia from the metastable tetragonal phase to the stable monoclinic phase within the near vicinity of the crack tip would suppress primary crack extension and improve fracture toughness. In ceramic materials, an increase of toughness provides high mechanical performance.
Compared to other ceramic materials, however, since zirconia has a relatively low hardness of about 1200 kg/mm.sup.2, the zirconia-modified ceramic material, though it is satisfactory in mechanical strength, has a drawback in that its hardness is lowered. For ceramics for which high hardness is another important requirement, for example, for cutting tools, therefore, only a limited amount of zirconia can be added. Development of alumina-based ceramics that are characterized both by high mechanical strength and high hardness are thus needed.